Apparatus for controlling the position of work rolls



June 25, 1968 A. D. REINHARDT ET AL 3,389,588

APPARATU FOR CONTROLLING THE POSITION OF WORK ROLLS Filed March 9, 1965Lg/ I For" sauna:

INVENTORS ANTHONY D. RE/lV/IARDT and ROBERT C. SL/F/(A United StatesPatent 3,389,588 APPARATUd FQR CGNTROLLING THE. PGSHTEUN OF WGRK ROLLSAnthony D. Reinhardt, South Holland, and Robert C.

Slifha, Cicero, ill assignors to United States Steel Corporation, acorporation of Delaware Filed Mar. 9, 1965, Ser. No. 433,274 3 Claims.(Cl. 72-3) ABSTRACT tlF THE DESQLOSURE An apparatus for controlling theposition of work rolls in a mill is disclosed which includes means toobtain a signal related to the spacing between the work rolls, means toprovide a command signal proportional to desired roll spacing and meansto operate a fluid system responsive to a signal related to thedeviation between actual and desired roll spacing so as to adjust theroll spacing.

The present invention relates to an apparatus for controlling theposition of work rolls in a rolling mill. More particularly, theinvention involves adjusting the spacing between the work rolls so as tomaintain an approximate desired roll gap.

In recent years, there has been emphasis on improving the quality ofrolled products. As a result, greater efforts have been made to moreaccurately control product thickness during rolling. Conventionally, thethickness of the product has been determined by measuring the productafter rolling and making mill adjustments as needed. The presentinvention contemplates maintaining continuous surveillance of the rollgap and making instantaneous mill adjustments to compensate forundesirable deviations.

An outstanding advantage of the invention is the relative simplicity ofthe equipment to measure the position of work rolls in a rolling mill.The invention is particularly useful in slab mills and in other millswhere relatively thick product is rolled. The system employed formeasuring and controlling the roll position can maintain roll spacingwithin a tolerance of $0.025. Although not sufliciently accurate forthin gauge strip, the system according to the invention is well-suitedfor use on rolling mills in which relatively thick product such as slabsare rolled.

.In addition to the above, the invention is particularly useful inconjunction with continuous metal casting oper ations. In continuouscasting, a continuous metal column of metal is produced which is passedthrough rolls which should be maintained at a preselected roll spacing.In spite of continual variation in the roll separating forces caused bychanges in the thickness and temperature of the metal column enteringthe rolls, the present invention can be employed to maintain thepreselected roll gap with sufficient accuracy to produce a more uniformproduct.

Other advantages of the invention will be made more apparent by thefollowing description in conjunction with the drawing which is aschematic diagram illustrating a preferred embodiment of the invention.

In the drawing, a Z-high rolling stand is shown, comprising top andbottom rolls l2 and M, respectively, having shafts mounted in rollchocks 12a and 12b and 14a and 141), respectively. The roll checks inturn are supported in a mill housing It) wherein they may be movedvertically to adjust the roll gap, i.e. spacing, between the rolls l2and M. in the preferred embodiment illustrated, the position of top roll12. is fixed within the mill housing lti, but the roll chochs 14a andltd!) of the bottom roll are supported by fluid-operated assemblies Zitaand Z lb to raise and lower the bottom roll.

3,339,588 Patented June 25, 1968 The spacing between the rolls iscontrolled by means of an electrical system which measures the roll gapand energizes the hydraulic system to affect movement of bottom roll 14as needed (up or down) so as to maintain the desired roll spacing. Thisis accomplished in the preferred embodiment by means of a transducer 22connected to a recorder 50 whose indicator arm 51 is mechanically linkedto the slider arm 52 of a retransmitting potentiometer '2 which is inturn connected to a device 54 which compares the magnitude of twoelectrical signals and energizes the proper fluid system to raise orlower the bottom work roll to maintain the desired roll gap. Alsoconnected to device 54-, which may be a bridgebalance relay as hereinafter described, is a set-point potentiometer 56 whose slider arm 56'may be manually set to issue a signal to device 54 proportional to thedesired roll spacing.

The roll gap is varied by moving roll 14 by means of the fiuidoperatedcylinder-ram assemblies 29a and 201). To operate the cylinder-ramassemblies, a pump 24 continuously circulates fluid to the storagereservoir 26 through a control valve 28 which is positioned in fluidline Stl. The control valve 28, which is preferably an air-actuatedvalve produced by Republic Mfg. Co., model No. 831-1, is normally opento permit the circulation of fluid to the reservoir 26 and is closed byintroducing air through line 32 via solenoid valve 34 (connected to anair supply not shown). The air-actuated control valve 28 may be closedby solenoid-operated valve 34. The solenoid valves used herein may bemodel CC20025A made by Hannifin. When valve 23 is closed, fluid frompump 24 is forced to flow through line 36 and through check valve 38into the flow divider 4d which distributes the fluid flow into two equalcomponents which are diverted to the two fluid-operated ram assemblies aand 20b to cause the roll 14 to move upwardly and thereby decrease theroll gap.

The bottom roll is lowered by energizing solenoid-operated valves 48aand dtib thereby permitting pump 60 to force pilot fluid through lines49a and 4912 thereby applying force to hydraulic actuators which. inturn open decompression valves Ma and 44b to allow fluid from ramassemblies 201: and 20b to escape through lines 46a and 46b to thereservoir 26, thus lowering roll 14. The solenoids 47a and 47b ofsolenoid-operated valves 48a and 48b together with the solenoid ofsolenoid-operated valve 34 are energized and de-energized by controlrelays and 57 which are contained within the bridge-balance relay 54.Relays 55 and 57 are energized by power from a transistorized amplifieralso contained within bridgebalance relay 54.

In operation, the roll gap measuring device 22 which may be any suitabletransducer but in the preferred embodiment is a spring-loaded reel-typeprecision potentiometer, with its wire connected between the rollchocks, receives a constant input signal and produces an output signalapproximately proportional to the existing roll gap. The signal sent bydevice 22 is only approximately proportional to the roll spacing becauseit actually measures the spacing between the roll chocks which may beslightly different than the spacing between the rolls. Spacing be tweenthe rolls will vary largely due to rolling forces which change therelative positions of the roll chocks which changes are proportional tochanges in the roll gap but, in addition, because of roll Wear,deflection, etc; these latter changes will not be reflected in thesignal issued by the potentiometer 22. However, it has been found thatan arrangement as illustrated can be satisfactorily operated within$0.625 of actual roll spacing. This tolerance is more than satisfactoryfor a relatively large roll gap such as would be used in rolling slabs.The signal issued from potentiometer 22 which is therefore approximatelyproportional to the roll gap, is received by a strip recorder 50 whichprovides a continuous record of changes in the roll spacing. Anysuitable recorder may be employed such as the Minneapolis-Honeywellcontinuous-balance potentiometer type. As the roll gap and the relativepositions of the roll chocks 12a and 14a vary, the reel of thepotentiometer 22 is likewise rotated by the wire connection between thechocks to change the valve of the signal to the recorder. Simultaneouslyactuated is a circuit comprising a set-point potentiometer 56 and aretransmitting potentiometer 52 both of which are connected to asuitable device 54- for comparing values and algebraically summarizingtwo electrical signals. One preferred such device for comparing valuesof two electrical signals is a bridge-balance relay produced by theMinneapolis-Honeywell Regulator Company, Minneapolis, Minn., identifiedas R7103C and described in a publication by the manufacturer identifiedas 95-5420.

The set-point potentiometer 56 has an adjustable slider arm and dial 56'to permit a manual setting of potentiometer 56 so as to provide anelectrical signal to the bridge-balance relay 54 proportional to thedesired roll spacing. The potentiometer is properly calibrated for thispurpose. The retransmitting potentiometer 52 has a slider arm 52' thatis mechanically linked with the arm or pen of the recorder 50 so that itassumes a position in accordance with the existing roll gap as indicatedon the recorder. Any suitable recorder may be used such as thecontinuous-balance potentiometer type made by Minneapolis-Honeywell. Inthis way, the potentiometer 52 provides a signal to the relay 54approximately proportional to the existing roll gap. The bridge-balancecontrol relay contacts receive an input from a power source throughlines L and L and compare the signal from the set-point potentiometer 56to the signal from the retransmitting potentiometer 52. These signalsare of equal value when the roll spacing conforms with the desired rollgap. In that event, the bridge-balance relay 54 Will have both of itscontrol relays, 55 and 57 and their respective circuits 54x and 54z,each of which include common line 54y deenergized, thereby causing nochange in the roll gap. If, however, the roll gap is greater than thatdesired, the bridge-balance relay will be unbalanced and will energizecontrol relay 57 which, when closed, connects the solenoid 35 associatedwith solenoid-operated valve 34 with the line source and the solenoid isenergized to operate the valve. When valve 34 is opened, it permits airto enter through line 32 closing the air-actuated control valve 28.

Fluid is then forced by pump 24 through line 36, passed thespring-loaded check valve 38 into the flow divider 40 and then intolines 40a and 40b. The fluid passes check valves 41a and 41b to enterthe cylinder-ram assemblies 20a and 20b, thereby raising roll chocks 14aand 14b and work roll 14. This action continue-s until the desired rollgap is achieved at which time the slider arm 52 of the retransmittingpotentiometer 52 is at a setting such that the signals from thispotentiometer and the set-point potentiometer will balance in the relay54 and the control relay 57 becomes de-energized. De-energizing controlrelay 57 causes the solenoid-operated valve 34 to shift, permitting airto open valve 28 and resumes the flow of fluid through line 30 to thereservoir 26, thereby halting the flow of fluid into the cyinder-ramassemblies 20a and 20b.

If the existing roll gap is less than the desired roll spacingestablished by the slider arm of the set-point potentiometer 56, thebridge-balance relay energizes the normally opened relay 55. 'In sodoing, solenoids 47a and 47b of solenoid-operated valves 48a and 4%!)are electrically connected with the line source and the valves 48a and48b are operated to open pilot-operated decompression valves 44a and44b. This, as previously described, causes fluid to be exhausted fromthe cylinder-ram assemblies 20a and 20b, thereby causing thecylinder-rams and bottom roll to lower and increase the roll spacing.This action continues until the selected roll gap is achieved asindicated by the slider arm of the retransmitting potentiometer 52. Thesignals from the retransmitting potentiometer and set-pointpotentiometer then balance in the bridge-balance relay, and no signal isproduced across 54x and S-tz. As these signals become equal, bridge 54is balanced and relay 55 is opened and the solenoids 47a and 47b arede-energized, closing valves 811 and 48b. This directs pilot flow frommotor-operated pump 69 to the reservoir and allows lines 49a and 49b todrain and stops the flow of fluid from the cylinderram assemblies 20aand 20b to the reservoir '26 and the roll gap is thereby maintained atthe preselected setting.

It is apparent from the above that various changes and modifications maybe made without departing from the invention. The fluid-operating systememployed in conjunction with the circuitry for sensing the approximateposition of the Work rolls with respect to each other has been found tobe effective for instantaneous mill adjustments. The term fluid-operatedsystem, of course, refers generally to hydraulic systems. Although onetype of valve responsive to electrical signals has been shown, i.e. thesolenoid-operated valves, other valves operating under the sameprinciple may be similarly employed, preferably other low torque rotarydirectional valves. In this connection it should be noted that alternateequipment performing similar functions may be readily substitutedthroughout the system described herein. Thus, for example, summing orbi-stable amplifiers may be used in lieu of the bridge-balance relay.Similarly other transducers, or indeed, any device which translatesmechanical displacement into a proportional signal, electrical orotherwise, may be used in place of the spring-loaded potentiometer 22.

In the preferred embodiment described herein, a recorder is used tomaintain a record of roll changes. However, it is apparent that therecorder may be omitted and, moreover, the potentiometer 22 may bedirectly connected to the bridge-balance relay 54, thereby alsoomitting, if desired, retransmitting potentiometer 52.

We claim:

1. Apparatus for controlling the position with respect to each other ofwork rolls in a rolling mill comprising means to obtain a first signalapproximately proportional to the spacing between work rolls in arolling mill, means to provide a command signal proportional to thedesired roll spacing, means to compare said first signal and saidcommand signal, a fluid-operated system responsive to said last-namedmeans for increasing and decreasing roll spacing so that a desiredapproximate roll spacing may be maintained.

2. An apparatus for controlling the position with respect to each otherof work rolls in a rolling mill comprising upper and lower work rolls,support means for said work rolls, fluid-operated rams positioned at thesupports of at least one work roll in said rolling mill adapted to raiseand lower said roll, means to provide a controlled supply of fluid tosaid fluid-operated rams, means to evacuate a controlled quantity offluid from said fluid-operated rams, means to obtain a signalapproximately proportional to the spacing between the rolls, meansresponsive to said signal for energizing and de-energizing said means tosupply fluid to said rams and said means to evacuate fluid from saidrams whereby a desired roll spacing is maintained.

3. An apparatus for controlling the position with respect to each otherof work rolls in a rolling mill having upper and lower work rolls withthe roll ends mounted in roll chocks and supported in a mill housingcomprising a fluid-actuated cylinder-ram assembly positioned beneath theroll chock at each end of the bottom roll for raising and lowering saidroll chocks and roll, first means to supply a controlled quantity offluid to said cylinderram assemblies to raise said bottom roll andsecond means to withdraw a controlled quantity of fluid from saidcylinder-ram assemblies to lower said bottom roll, means to obtain afirst signal proportional to thespacing between the roll chocks of thetop and bottom rolls, means to provide a command signal proportional tothe desired roll spacing, means to compare said first signal and saidcommand signal and to energize one of said first means and said secondmeans to raise or lower the bottom work roll until said first signal andsaid command signal balance.

References Cited UNITED STATES PATENTS 0 GERALD A. DOST, PrimaryExaminer.

